A method of Ga removal from a specimen fabricated on MEMS-based chip for in-situ transmission electron microscopy

Abstract In-situ transmission electron microscopy (TEM) holders, which are widely used in recent years, employ a chip-type specimen stage. To prepare the specimen on the microelectromechanical system (MEMS)-based chip, focused ion beam (FIB) and ex-situ lift-out (EXLO) techniques has been widely used. However, thin foil specimens prepared using the FIB inevitably contain the contamination induced by Ga+ ions. In particular, when the specimen is heated for real time observation, it is observed that Ga+ ions influence the reaction or aggregate in the protection layer. An effective method of removing the Ga residue is demonstrated using Ar+ ion milling within FIB. In the case of lifting the thin foil specimen from the trench by the EXLO technique, Ga still remained even if Ar+ ion milling was conducted. To avoid this problem, the thin foil specimen was attached to FIB lift-out grid, performing Ar+ ion milling, and then transferred to a MEMS chip using EXLO technique. The removal of the Ga residue was confirmed using energy dispersive spectroscopy (EDS).